Castillo et al.: Recruitment variation in Eopsetta jordani 



485 



crease in parental-stock size, as negative trends be- 

 tween YCS and potential egg production were ob- 

 served for year classes from 1970 to 1977 (Area 2B: 

 r=-0.81, P<0.05; Area 3A: r=-0.57, P<0.20; Fig. 4A). 

 Examination of the attendant filtered series did not 

 support a density-dependent relationship when the 

 size of the parental stock was large (e.g. Ricker, 1954; 

 Area 2B: r=0.21, Area 3A: r=0.07; Fig. 4B). 



Environmental-YCS fluctuations (1959-1977) 



Alongshore transport indices 



1 Mean sea level height The strongest northward 

 and southward coastal flow generally coincide with 

 the highest and lowest mean sea levels off Oregon 

 (Huyer et al., 1975). Long-term seasonal sea levels 

 indicated that stronger northward and southward 

 flows from 1959 to 1977 occurred in winter and sum- 

 mer, respectively (Appendix A). Correlations between 

 YCS and mean sea level were highest in winter for 

 both study areas (Fig. 5A). The attendant filtered 

 series showed lower but consistent correlations for win- 

 ter ( Fig. 6A). Thus, recruitment strength of petrale sole 

 seems to be associated with interannual variation in 

 nearshore northward transport during winter. 



2 Northward Ekman transport This index indi- 

 cates the alongshore flow of surface mixed layers 

 driven by wind stress. Unlike sea level height, there 

 was no correlation between northward Ekman trans- 

 port and YCS (Figs. 5B and 6B). The four long-term 

 seasonal means of this index indicated predomi- 

 nantly negative northward transport (i.e. southward 

 transport) of surface waters at offshore areas (45°N- 

 125°W, Appendix A). 



3 Northward Sverdrup transport This index mea- 

 sures alongshore transport over the entire water col- 

 umn by adding geostrophic flow to Ekman transport. 

 For nonwinter seasons, the long-term seasonal means 

 of this index showed southward transport of offshore 

 waters (45°N-125°W, Appendix A). Northward 

 Sverdrup transport and YCS were not consistently 

 correlated (Figs. 5C and 6C). 



Offshore Ekman transport The long-term seasonal 

 means of this index indicated average offshore trans- 

 port of surface waters and upwelling from spring to 

 summer followed by onshore transport and down- 

 welling from fall to winter (Appendix A). Winter off- 

 shore Ekman transport and YCS showed clear and 

 consistent negative correlations in 

 both study areas ( Figs. 5D and 6D ). 



Cube of wind speed This in- 

 dex reflects the turbulence 

 transferred to the sea surface by 

 the wind (Niiler and Kraus, 

 1977). Although cube of wind 

 speed was correlated with YCS 

 for winter and spring (Figs. 5E 

 and 6E ), these correlations were 

 largely explained by onshore 

 Ekman transport during this 

 period. Moreover, correlations 

 for spring vanished in both ar- 

 eas when March was excluded 

 from the analyses. Thus, cube 

 of wind speed seems to be spu- 

 riously correlated with YCS. 



Sea surface temperature Long- 

 term seasonal means of sea sur- 

 face temperature increased 

 from winter through summer 

 and decreased from fall through 

 winter (Appendix A). Correla- 

 tions between YCS and sea sur- 

 face temperatures for winter 

 and spring showed high positive 



